1. Field of the Invention
This invention relates to a method for manufacturing a test paper and, more particularly, to a method for manufacturing a test paper, which is flexible, portable, high sensitive and can be extensively applied for the detection of pesticides used in fruit, drink contaminants, bio-molecular or regular chemical by utilizing an inkjet printing process, a method for using thereof and a chemical composition used in the abovementioned manufacturing method.
2. Description of the Related Art
Recently, “Food Safety” has become a serious issue in the life. Everyone questions whether the food and the drink we eat and drink everyday contains harmful or illegal additives. For example, melamine (C3H3N6) will affect the urinary system and is not allowed above a certain ‘country specific’ limit. According to the FDA in US, Tolerable Daily Intake (TDI) of melamine is 0.63 mg/Kg per day. However, melamine is used as a food additive to fake an enhanced protein content in the food and thus the food with low protein content and quality can pass the test of the food inspection institute.
Therefore, a suitable analytical method is necessary in order to manage the food safety. Generally speaking, current analytical methods for testing prohibited substances are mainly HPLC-based that are time-consuming, expensive, and labor-intensive, requiring complex procedures of sample pretreatment and well-trained technicians to operate them. In addition, low temperature fluorescence can also be used to inspect the abovementioned food with low quality. However, the sensing was mostly done on labeled molecules, which involves complexity and high precision techniques.
Raman spectrum, relies on inelastic scattering of light by vibrating molecules, and has been widely used to detect chemicals, such as diamond, medicine, and bio-molecule as well as the tool for studying molecules adsorbed on the surface. There are some advantages of Raman spectroscopy that the traditional clinical biochemical assay does not have. Further, Raman spectroscopy, different with other near-IR spectroscopy, is not greatly affected by water. Being a vibrational spectroscopy it suppresses the electronic transitions resulting in fluorescence. The technique will be very useful to apply on the detection of bio-molecules. However, Raman signals are quite weak which is restricted by the small Raman scattering cross section. In addition, as the concentration of general biomolecule is low, it is difficult to use Raman spectroscopy for bio detection.
It's worth noting that the application of Raman spectroscopy became more and more important due to the invention of Surface Enhanced Raman Scattering (“SERS” hereinafter). SERS signals arise from the molecules adsorbed on special rough metal surfaces that produces a huge enhancement (surface enhancement) of the previously weak Raman signal. Hence, this technique can detect very low concentrations of bio-samples or even single molecule because of the strongly enhanced signal. SERS offers a technique of observing and understanding the molecular structure and vibrational energy levels which are finger-prints for Raman active molecules. Basically, the single molecule detection techniques include fluorescence, near-field optics, far-field optics and evanescent wave. Compared to fluorescence method, SERS can obtain much more information of molecular vibration and can be applied on non-fluorescent molecules. Therefore, this technique not only can be widely used in bio-sensing, but also can be applied to ensure food safety.
Although various applications for SERS have been studied, but it is still limited by the choice of a simple and effective substrate and the roughness of the metal nanoparticles required for the surface enhancement. Moreover, the intensities of the Raman spectra and the orientation of the Raman active molecules are strongly correlated to result in larger errors and non-reproducible measurements qualitative analysis very difficult.